As technologies evolve, complementary metal-oxide semiconductor (CMOS) image sensors are attracting more attention due to performance advantages. For example, CMOS image sensors can provide higher image acquisition rates, lower operating voltages, lower power consumption and greater noise immunity. A CMOS image sensor usually comprises an array of light-sensing elements or pixels. Each of the pixels is configured to convert received photons into electrons. Additionally, the CMOS image sensor comprises circuitry to transform the electrons into electrical signals. The electrical signals are then processed to generate an image of a subject scene.